Chainrings and Crank Assemblies

ABSTRACT

A chainring includes a first section having consecutive first teeth. Each of the first teeth includes a first load flank surface having a first wear resistance. The chainring also includes a second section coupled to the first section. The second section includes consecutive second teeth. Each of the second teeth includes a second load flank surface having a second wear resistance greater than the first wear resistance. The consecutive second teeth span an arc length corresponding to between one twelfth and one third of a circumference of a pitch circle of the chainring.

BACKGROUND OF THE INVENTION

1. Field of the Background

This disclosure relates to bicycle drive trains and, more particularly,to crank assemblies and chainrings.

2. Description of the Background

A drive train of a bicycle often includes a chain operatively coupling acrank assembly to a sprocket disposed on a rear wheel of the bicycle.The crank assembly typically employs one or more chainrings and twocrank arms. During use of the bicycle, the user applies force to pedalscoupled to the crank arms to rotate the chainring. As a result, thechainring drives a chain, which rotates the rear wheel. During operationof the chainring, the chainring experiences wear.

SUMMARY

According to one aspect, a chainring includes a first section havingconsecutive first teeth. Each of the first teeth includes a first loadflank surface having a first wear resistance. The chainring alsoincludes a second section coupled to the first section. The secondsection includes consecutive second teeth. Each of the second teethincludes a second load flank surface having a second wear resistancegreater than the first wear resistance. The consecutive second teethspan an arc length corresponding to between one twelfth and one third ofa circumference of a pitch circle of the chainring.

According to another aspect, a chainring includes a first tooth having afirst load flank surface of a first wear resistance. The chainring alsoincludes a second tooth having a second load flank surface of a secondwear resistance greater than the first wear resistance. The chainringfurther includes a third tooth disposed consecutively with the secondtooth, the third tooth having a third load flank surface of the secondwear resistance. The second tooth has a different thickness than thethird tooth.

According to another aspect, a crank assembly includes a chainringhaving first teeth and second teeth. The first teeth each include afirst load flank surface of a first wear resistance. The second teetheach include a second load flank surface of a second wear resistancegreater than the first wear resistance. The crank assembly also includesa crank arm coupled to the chainring. The second teeth are consecutivelydisposed on the chainring between more than 60 degrees and less than 110degrees relative a longitudinal axis of the crank arm in a directionopposite a driving direction.

According to another aspect, a crank assembly includes a crank arm andonly one chainring coupled to the crank arm. The chainring includes afirst tooth and a second tooth. The first tooth includes a first loadflank surface having a first wear resistance. The second tooth includesa second load flank surface having a second wear resistance greater thanthe first wear resistance. The second tooth is in a position on thechainring relative to the crank arm that is to enable the second toothto apply a maximum force to a chain during a maximum torque portion of apedaling cycle of the crank a

According to another aspect, a chainring has a body having a first toothand a second tooth. The first tooth has a first load flank surface of afirst wear resistance. The chainring also includes an insert coupled tothe second tooth and forming a second load flank surface of the secondtooth. The second load flank surface has a second wear resistancegreater than the first wear resistance.

According to another aspect, a crank assembly has a first section of achainring including first teeth of a first material. The crank assemblyalso includes a second section of the chainring coupled to the firstsection. The second section includes second teeth of a second materialdifferent than the first material. The crank assembly further includes acarrier including an arm overlapping the second section of thechainring.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of an exemplary bicycle, which mayemploy the example chainrings and crank assemblies disclosed herein;

FIG. 2 is a graph representative of torque outputs of a rider of thebicycle of FIG. 1 during a pedaling cycle of a crank assembly;

FIGS. 2A-2C illustrate various angular positions of the crank assemblyof FIG. 2;

FIG. 3 is an outboard side, perspective view of a crank assembly;

FIG. 4 is a top plan view of a chain, which may be driven by the crankassembly of FIG. 3 ;

FIG. 5 is an outboard side, perspective view of a chainring of the crankassembly of FIG. 3 engaging the chain of FIG. 4;

FIG. 6 is a cross-sectional view of an inner link tooth, which may beemployed by the chainring of FIG. 5;

FIG. 7 is a cross-sectional view of an outer link tooth, which may beemployed by the chainring of FIG. 5;

FIG. 8 is a cross-sectional view of an alternative outer link toothdisclosed herein;

FIG. 9 is a cross-sectional view of another alternative outer link toothdisclosed herein;

FIG. 10 is an outboard side elevational view of the crank assembly ofFIG. 3;

FIG. 11 is an outboard side view of the chainring of FIG. 10;

FIG. 12 is another outboard side view of the chainring of FIG. 10;

FIG. 13 is another outboard side view of the chainring of FIG. 10 havingtwo sections of the chainring decoupled from a body of the chainring;

FIG. 14 is an inboard side view of one of the chainring of FIG. 13;

FIG. 15 is an inboard side, perspective view of one of the sectionsdecoupled from the chainring of FIG. 13;

FIG. 16 is an outboard side, perspective view of another embodiment of achainring, which may be employed to implement any of the crankassemblies disclosed herein;

FIG. 17 is an outboard side, exploded partial perspective view of thechainring of FIG. 16;

FIG. 18 is cross-sectional, partial perspective view of the chainringtaken along line 18-18 of FIG. 16;

FIG. 19 is an outboard side elevational view of yet another embodimentof a crank assembly;

FIG. 20 is a cross-sectional view of a chainring of the crank assemblyof FIG. 19 along line 20-20 of FIG. 19;

FIG. 21 is an outboard side, perspective view of another embodiment of achainring disclosed herein, which may be used to implement any of thedisclosed crank assemblies; and

FIG. 22 is an outboard side, perspective view of still anotherembodiment of a chainring disclosed herein, which may be used toimplement any of the crank assemblies disclosed herein.

Other aspects and advantages of the embodiments disclosed herein willbecome apparent upon consideration of the following detaileddescription, wherein similar or identical structures have similarreference numerals.

DETAILED DESCRIPTION

FIG. 1 illustrates an example bicycle 100, which may be used toimplement the crank assemblies and chainrings disclosed herein. In theillustrated embodiment, the bicycle 100 includes a frame 102, handlebars104, and a seat 106. The bicycle 100 also includes a first or frontwheel 108 and a second or rear wheel 110. The bicycle 100 includes adrive train 112. The drive train 112 of FIG. 1 includes a crank assembly114, a gear cluster or cassette 116, and a chain 118 operativelycoupling the crank assembly 114 to the cassette 116. The crank assembly114 is rotatably coupled to the frame 102, and the cassette 116 isnon-rotatably coupled to the rear wheel 110 in the drive direction.

In the illustrated embodiment, the crank assembly 114 includes a firstpedal 120, a second pedal 122, a first crank arm 124, a second crank arm(see, e.g., FIG. 3), a carrier 126, a first chainring 128, and a secondchainring 130. Although the example crank assembly 114 has twochainrings (i.e., the first chainring 128 and the second chainring 130),other crank assemblies disclosed herein have different numbers ofchainrings (e.g., 1, 3, 4, etc.). For example, the crank assembly 300 ofFIG. 3 has only one chainring.

The first pedal 120 is rotatably coupled to the first crank arm 124. Thesecond pedal 122 is rotatably coupled to the second crank arm. In theillustrated embodiment, the first crank arm 124 and the second crank armare non-rotatably coupled to the carrier 126, and the carrier 126 isnon-rotatably coupled to the first chainring 128 and the secondchainring 130. In FIG. 1, the first chainring 128 is selectivelyengaging the chain 118. However, the second chainring 130 mayselectively engage the chain 118. For example, the drive train 112 ofFIG. 1 includes a front derailleur 132 to move the chain 118 out ofengagement with the first chainring 128 and into engagement with thesecond chainring 130. The front derailleur 132 may also move the chain118 out of engagement with the second chainring 130 and into engagementwith the first chainring 128. A rear derailleur 134 moves the chain 118between a plurality of sprockets of the cassette 116.

FIG. 2 is a graph 200 representative of torque outputs of a rider of thebicycle 100 during a pedaling cycle of the crank assembly 114. The graph200 is also representative of the torque outputs of a rider of a bicycleemploying the crank assemblies and chainrings disclosed below withreference to FIGS. 3-22. Thus, the following description of thefollowing pedaling cycle is also applicable to the crank assemblies andchainrings of FIGS. 3-22.

In the illustrated embodiment, the pedaling cycle of the crank assembly114 occurs when the rider of the bicycle 100 pedals the first crank arm124 by 180 degrees from a substantially vertical, top or first position202 (see FIG. 2A) to a substantially vertical, bottom or second position204 (see FIG. 2C) in a driving direction DD. In the illustratedembodiment, a peak or maximum torque output during the pedaling cycleoccurs during a maximum torque portion of the pedaling cycle in whichthe first crank arm 124 is in or near a third or horizontal position 206(see FIG. 2B) as the rider pedals the first crank arm 124 from the firstposition toward the second position. Looking to FIG. 2, the maximumtorque portion of the pedaling cycle occurs between 60 and 100 degrees.A minimum torque output occurs during at least one of an initial minimumtorque portion of the pedaling cycle in which the first crank arm 124 isnear or in the first position 202 or a subsequent minimum torque portionof the pedaling cycle in which the first crank arm 124 is near or in thesecond position 204 as the rider pedals the first crank arm 124. As usedin this patent, the verbs “pedals” and “pedaling” means applying forceto a crank arm (e.g., the first crank arm 124 of FIG. 1) via a pedal(e.g., the first pedal 120) to rotate a chainring (e.g., the firstchainring 128 and/or the second chainring 130) to drive a chain (e.g.,the chain 118) of a bicycle.

FIGS. 3-5 illustrate one embodiment of a crank assembly 300, which maybe used to implement the example bicycle 100 of FIG. 1. In theillustrated embodiment, the crank assembly 300 includes only onechainring 302. The chainring 302 engages a chain 304 (see FIGS. 4 and5). With reference to FIG. 3, the crank assembly 300 also includes afirst crank arm 306 and a second crank arm 307 coupled to a carrier 308.The second crank arm 307 and the carrier 308 may be form as one piece orseparate. The second crank arm 307 is shown schematically in FIG. 3. Thecarrier 308 is coupled (e.g., nonrotatably coupled) to the chainring302. The crank assembly 300 is a mirror image of the first crank arm306.

In this embodiment, the chainring 302 includes a body 310 having aperiphery 312. The chainring 302 also includes teeth 314 disposed on theperiphery 312 of the body 310 for engagement with the chain 304. In theillustrated embodiment, the first crank arm 306 of FIG. 3 issubstantially straight or linear and has a first longitudinal axis 316.Force applied to the first crank arm 306 in a driving direction DI)rotates the chainring 302 in the driving direction about an axis ofrotation 317. As a result, the chainring 302 draws over and advances thechain 304 via the teeth 314. The second crank arm 307 may be coupled tothe carrier 308 such that a second longitudinal axis 318 of the secondcrank arm 307 is parallel to the longitudinal axis 316 of the firstcrank arm 306. In such embodiments, the chainring 302, the first crankarm 306, and the second crank arm 307 may rotate about the axis ofrotation 317.

FIG. 4 is a top plan view of the chain 304, which may be driven by thechainring 302 of FIG. 3. The chain 304 has a central, longitudinal axis319. The chain 304 includes outer chain links 320 and inner chain links322. The inner chain links 322 are pivotally mounted on and coupled tothe outer chain links 320 by pins 324. The outer chain links 320 arealternatingly interleaved with the inner chain links 322.

The outer chain links 320 have paired outer link plates 326 and theinner chain links 322 have paired inner link plates 328. Rollers 330 arearranged around the pins 324. The plates 326, 328 are provided withholes 332, and the pins 324 extend through and project out of the holes332. In some embodiments, ends 334 of the pins 324 do not project out ofthe holes 332. In the illustrated embodiment, the pins 324 are rivetedto the outer link plates 326 and the inner link plates 328. The outerchain links 320 are interleaved with the inner chain links 322 to definealternating outer link spaces 336 and inner links spaces 338. The outerlink spaces 336 are openings defined by the outer link plates 326 andthe rollers 330. The inner link spaces 338 are openings defined by theinner link plates 328 and the rollers 330.

The inner link spaces 338 are rectangular shaped. The outer link spaces336 are “cross” or “plus-sign” shaped. A first distance or width W1between an opposing pair of the outer link plates 326 is greater than asecond distance or width W2 between an opposing pair of the inner linkplates 328. For example, the second widths W2 of the inner link spaces338 are substantially equal to a width of the rollers 330. The firstwidths WI of the outer link spaces 336 are substantially equal to a sumof the width of a roller 330 and the thicknesses of the two adjacentinner link plates 328.

FIG. 5 is an enlarged, perspective view of the teeth 314 of thechainring 302 of FIG. 3 engaging the chain 304 of FIGS. 3 and 4. In theillustrated embodiment, each of the teeth 314 has one of twoconfigurations. Each of the teeth 314 having a first configuration arereferred to in this disclosure as outer link teeth 340. Each of theteeth 314 having a second configuration are referred to in thisdisclosure as inner link teeth 342. The outer link teeth 340 each have ashape and a size corresponding to the outer link spaces 336. The outerlink teeth 340 are to be received in only the outer link spaces 336 ofthe chain 304 during operation of the crank assembly 300. The inner linkteeth 342 have a shape and a size corresponding to the inner link spaces338. The inner link teeth 342 are to be received in only the inner linkspaces 338 of the chain 304 during operation of the crank assembly 300.Thus, in the illustrated embodiment, the outer link teeth 340 alternatewith the inner link teeth 342 along the periphery 312 of the chainring302. When the chain 304 engages the chainring 302, the rollers 300 ofthe chain 304 contacting the teeth 314 lie along a pitch circle 344 ofthe chainring 302. Each of the outer link teeth 340 has a first top land346. Each of the inner link teeth 342 has a second top land 348. In theembodiment of FIG. 5, the first top lands 346 each have a greaterthickness than the second top lands 348.

FIG. 6 is a cross-sectional view of one of the inner link teeth 342 (“aninner link tooth 342”) taken from line 6-6 of FIG. 5, which is on aplane tangent to the pitch circle 344 of the chainring 302 and extendingthrough a center 350 of the inner link tooth 342. The inner link teeth342 are substantially similar or identical to each other. Therefore, thefollowing description of the inner link tooth 342 of FIG. 6 isapplicable to each of the other inner link teeth 342 of the chainring302. Therefore, to avoid redundancy, the other inner link teeth 342 arenot separately described herein.

The inner link tooth 342 has a rectangular cross-sectional shape fromthe perspective of FIG. 6. The inner link tooth 342 has a longitudinallength LT1. In the illustrated embodiment, the rectangularcross-sectional shape and a first tooth width. WO1 of the inner linktooth 342 substantially matches the rectangular shape and the secondwidth W2, respectively, of each of the inner link spaces 338 of thechain 304. For example, the inner link tooth 342 may fill or occupy overabout 75% of the second width W2 of one of the inner link spaces 338when the inner link tooth 342 is fully received in the inner link space338. In some embodiments, the inner link tooth 342 may fill or occupyover about 80% of the second width W2 of one of the inner link spaces338 when the inner link tooth 342 is fully received in the inner linkspace 338. In some embodiments, the inner link tooth 342 may fill oroccupy over about 85% of the second width W2 of one of the inner linkspaces 338 when the inner link tooth 342 is fully received in the innerlink space 338. In some embodiments, the inner link tooth 342 may fillor occupy different amounts of the second width W2 of one of the innerlink spaces 338 when the inner link tooth 342 is fully received in theinner link space 338.

FIG. 7 is a cross-sectional view of an outer link tooth 400, which maybe used to implement one or more of the outer link teeth 340 of FIGS. 3and 5. The cross-sectional view of FIG. 7 is taken from line 7-7 of FIG.5, which is on a plane tangent to the pitch circle 344 of the chainring302 and extending through a center 402 of the outer link tooth 400. Theouter link tooth 400 has a second longitudinal length LT2. In theillustrated embodiment, the second longitudinal length LT2 of the outerlink tooth 400 is substantially the same as the first longitudinallength LT1 of the inner link tooth 342 of FIG. 6. In other embodiments,the second longitudinal length LT2 of the outer link tooth 400 isdifferent than the first longitudinal length LT1 of the inner link tooth342.

The outer link tooth 400 of FIG. 7 has a body 404 and an outboardprotrusion 406 extending from an outboard side 408 of body 404. The body404 of the outer link tooth 400 of FIG. 7 does not have a protrusionextending from an inboard side 410 of the body 404. The outboardprotrusion 406 facilitates engagement between the outer link tooth 400and the chain 304. In the illustrated embodiment, the outer link tooth400 of FIG. 7 has a second tooth width WO2 greater than the first toothwidth WO1. In the illustrated embodiment, the body 404 of the outer linktooth 400 has the first tooth width WO1 and the outboard protrusion 406has a first protrusion width WP1.

As a result, the outer link tooth 400 may fill or occupy over about 75%of the first width W1 of one of the outer link spaces 336 when the outerlink tooth 400 is fully received in the outer link space 336. In someembodiments, the outer link tooth 400 may fill or occupy over otheramounts (e.g., more than 80%, more than 85%, etc.) of the first width W1of one of the outer link spaces 336 when the outer link tooth 400 isfully received in the outer link space 336.

FIG. 8 is a cross-sectional view of another example outer link tooth500, which may be used to implement one or more of the outer link teeth340 of FIGS. 3 and 5. The cross-sectional view of FIG. 8 is taken fromline 7-7 of FIG. 5, which is on a plane tangent to the pitch circle 344of the chainring 302 and extending through a center 502 of the outerlink tooth 500. The outer link tooth 500 has the second longitudinallength LT2. In the illustrated embodiment, the second longitudinallength LT2 of the outer link tooth 500 is substantially the same as thefirst longitudinal length LT1 of the inner link tooth 342 of FIG. 6. Inother embodiments, the second longitudinal length LT2 of the outer linktooth 500 is different than the first longitudinal length LT1 of theinner link tooth 342.

The outer link tooth 500 of FIG. 8 has a body 504 and an outboardprotrusion 506 extending from an outboard side 508 of body 504. The body504 of the outer link tooth 500 of FIG. 8 also has an inboard protrusion510 extending from an inboard side 512 of the body 504. The outboardprotrusion 506 and the inboard protrusion 510 facilitate engagementbetween the outer link tooth 500 and the chain 304. In the illustratedembodiment, the outer link tooth 500 of FIG. 8 has a third tooth widthWO3 greater than the first tooth width WO1. In some embodiments, thethird tooth width WO3 is greater than the second tooth WO2. In theillustrated embodiment, the outboard protrusion 506 has the firstprotrusion width WP1, and the inboard protrusion 510 has a secondprotrusion width WP2 less than the first protrusion width WP1.

As a result, the outer link tooth 500 may fill or occupy over about 75%of the first width W1 of one of the outer link spaces 336 when the outerlink tooth 500 is fully received in the outer link space 336. In someembodiments, the outer link tooth 500 may fill or occupy over otheramounts (e.g., more than 80%, more than 85%, etc.) of the first width W1of one of the outer link spaces 336 when the outer link tooth 500 isfully received in the outer link space 336.

FIG. 9 is a cross-sectional view of another example outer link tooth600, which may be used to implement one or more of the outer link teeth340 of FIGS. 3 and 5. The cross-sectional view of FIG. 9 is taken fromline 7-7 of FIG. 5, which is on a plane tangent to the pitch circle 344of the chainring 302 and extending through a center 602 of the outerlink tooth 600. The outer link tooth 600 has the second longitudinallength LT2. In the illustrated embodiment, the second longitudinallength LT2 of the outer link tooth 600 is substantially the same as thefirst longitudinal length LT1 of the inner link tooth 342 of FIG. 6. Inother embodiments, the second longitudinal length LT2 of the outer linktooth 600 is different than the first longitudinal length LT1 of theinner link tooth 342.

The outer link tooth 600 of FIG. 9 has a body 604 and an outboardprotrusion 606 extending from an outboard side 608 of body 604. The body604 of the outer link tooth 600 of FIG. 9 also has an inboard protrusion610 extending from an inboard side 612 of the body 604. The outboardprotrusion 606 and the inboard protrusion 610 facilitate engagementbetween the outer link tooth 600 and the chain 304. In the illustratedembodiment, the outer link tooth 600 of FIG. 9 has a fourth tooth widthWO4 greater than the first tooth width WO1. In some embodiments, thefourth tooth width WO4 is greater than the second tooth width WO2. Inother embodiments, the fourth tooth width WO4 is greater than the thirdtooth WO3. In the illustrated embodiment, the outboard protrusion 606has the first protrusion width WP1, and the inboard protrusion 610 has afirst protrusion width WP1.

As a result, the outer link tooth 600 may fill or occupy over about 75%of the first width W1 of one of the outer link spaces 336 when the outerlink tooth 600 is fully received in the outer link space 336. In someembodiments, the outer link tooth 600 may fill or occupy over otheramounts (e.g., more than 80%, more than 85%, etc.) of the first width W1of one of the outer link spaces 336 when the outer link tooth 600 isfully received in the outer link space 336.

FIG. 10 depicts the crank assembly 300 in the second or horizontalposition. Thus, the longitudinal axis 316 of the first crank arm 306 ofFIG. 3 is horizontal from the perspective of FIG. 10. In the illustratedembodiment, the chainring 302 includes a first section 700, a secondsection 702, a third section 704, and a fourth section 706. In theillustrated embodiment, the first section 700 and the fourth section 706are unitary and/or are integrally formed with the body 310 of thechainring 302. For example, the first section 700, the fourth section706, and the body 310 may be stamped from a single piece of aluminumalloy. In the illustrated embodiment, the first section 700 includes apredetermined number of the teeth 314. For example, the first section700 of FIG. 10 includes nine of the teeth 314. In other embodiments, thefirst section 700 includes other numbers of the teeth 314 (e.g., 1, 2,3, 4, 5, 6, 7, 8, 10, 11, etc.). The teeth 314 of the first section 700are referred to herein as first teeth 708.

The first teeth 708 are disposed consecutively on the first section 700.Thus, the first teeth 708 are the outer link teeth 340 and the innerlink teeth 342 alternating with the outer link teeth 340. Therefore,consecutive teeth of the first teeth 708 have different thicknesses. Forexample, a first one of the first teeth 708 may be an inner link tooth342 having a first tooth width WO1, and a second one of the first teeth708 disposed consecutively with the first one of the first teeth 708 mayhave the fourth tooth width WO4 greater than the first tooth width WO1.

In the illustrated embodiment, the first teeth 708 and, particularly, afirst load flank surface 710 of each of the first teeth 708 have a firstwear resistance. As used in this disclosure, a load flank surface is asurface of a tooth (e.g., one of the teeth 314) that contacts a roller(e.g., the rollers 330) of a chain and applies force to the chain todrive the chain. In some embodiments, the first load flank surfaces 710of the first teeth 708 have a first smoothness, a first hardness, a wearresistant coating, and/or one or more additional and/or alternativecharacteristics enabling the first teeth 708 to have the first wearresistance. In the illustrated embodiment, the first teeth 708,including the first load flank surfaces 710, are heat treated, wroughtaluminum alloy. In other embodiments, the first teeth 708 and/or thefirst load flank surfaces 710 are other materials.

The second section 702 is coupled to the body 310 of the chainring 302.In the illustrated embodiment, the second section 702 includes a firstbracket 712 permanently coupled to the body 310 of the chainring 302.For example, a weld, a braze weld, bonding, and/or one or moreadditional and/or alternative fasteners may permanently couple the firstbracket 712 to the body 310. As used in this patent, “permanentlycoupled” means coupled in a manner that is intentionally difficult todecouple and/or intentionally cannot be decoupled without damaging orbreaking one or more components. In other embodiments, the first bracket712 is removably coupled to the body 310 of the chainring 302. Forexample, one or bolts and/or one or more additional and/or alternativefasteners may removably couple the first bracket 712 to the body 310 ofthe chainring 302. As used in this disclosure, “removably coupled” meanscoupled in a manner that is intentionally decoupleable.

The second section 702 includes a predetermined number of the teeth 314.In the illustrated embodiment, the second section 702 includes eight ofthe teeth 314. In other embodiments, the second section 702 includesother numbers of the teeth 314 (e.g., 1, 2, 3, 4, 5, 6, 7, 9, 10, 11,etc.). In the illustrated embodiment, the second section 702 has adifferent number of the 314 teeth than the first section 700. In otherembodiments, the second section 702 has the same number of the teeth 314as the first section 700. The teeth 314 of the second section 702 arereferred herein as second teeth 714. In the illustrated embodiment, thesecond teeth 714 are unitary and/or integrally formed with the firstbracket 712. In other embodiments, the second teeth 714 are coupled tothe first bracket 712.

The second teeth 714 are disposed consecutively on the second section702. Thus, the second teeth 714 are the outer link teeth 340 and theinner link teeth 342 alternating with the outer link teeth 340.Therefore, consecutive teeth of the second teeth 714 have differentthicknesses. For example, a first one of the second teeth 714 may be aninner link tooth 342 having a first tooth width WO1, and a second one ofthe second teeth 314 disposed consecutively with the first one of thesecond teeth 714 may have the fourth tooth width WO4 greater than thefirst tooth width WO1.

In the illustrated embodiment, the second teeth 714 and, particularly, asecond load flank surface 716 of each of the second teeth 714 have asecond wear resistance greater than the first wear resistance. In someembodiments, the second load flank surfaces 716 of the second teeth 714have a second smoothness smoother than the first smoothness, a secondhardness harder than the first hardness, a wear resistant coating,and/or one or more additional and/or alternative characteristicsenabling the second teeth 714 to have the second wear resistance. In theillustrated embodiment, the second teeth 714, including the second loadflank surfaces 716, are high carbon, alloyed steel. In some embodiments,the second teeth 714, including the second load flank surfaces 716, aretitanium alloy. In other embodiments, the second teeth 714 and/or thesecond load flank surfaces 716 are other materials. The second teeth maybe four times more wear resistant than the first teeth.

The third section 704 is also permanently coupled to the body 310 of thechainring 302. In the illustrated embodiment, the third section 704includes a second bracket 718 permanently coupled to the body 310 of thechainring 302. For example, a weld, a braze weld, bonding, and/or one ormore additional and/or alternative fasteners may permanently couple thesecond bracket 718 to the body 310. In other embodiments, the secondbracket 718 is removably coupled to the body 310 of the chainring 302.For example, one or bolts and/or one or more additional and/oralternative fasteners may removably couple the second bracket 718 to thebody 310 of the chainring 302.

The third section 704 includes a predetermined number of the teeth 314.In the illustrated embodiment, the third section 704 includes eight ofthe teeth 314. Thus, in the illustrated embodiment, the second section702 and the third section 704 have the same number of teeth. In otherembodiments, the third section 704 includes other numbers of the teeth314 (e.g., 1, 2, 3, 4, 5, 6, 7, 9, 10, 11, etc.). In some embodiments,the third section 704 has a different number of the teeth 314 than thesecond section 702. The teeth 314 of the third section 704 are referredto herein as third teeth 720. In the illustrated embodiment, the thirdteeth 720 are unitary and/or integrally formed with the second bracket718. In other embodiments, the third teeth 720 are coupled to the secondbracket 718.

The third teeth 720 are disposed consecutively on the third section 704.Thus, the third teeth 720 are the outer link teeth 340 and the innerlink teeth 342 alternating with the outer link teeth 340. Therefore,consecutive teeth of the third teeth 720 have different thicknesses. Forexample, a first one of the third teeth 720 may be an inner link tooth342 having a first tooth width WO1, and a second one of the third teeth720 disposed consecutively with the first one of the third teeth 720 mayhave the fourth tooth width WO4 greater than the first tooth width WO1.

In the illustrated embodiment, the third teeth 720 and, particularly, athird load flank surface 722 of each of the third teeth 720 have a thirdwear resistance greater than the first wear resistance. In someembodiments, the third wear resistance is greater than the second wearresistance. In other embodiments the third wear resistance is less thanthe second wear resistance. In still other embodiments, the third wearresistance is equal to the second wear resistance. In some embodiments,the third load flank surfaces 722 of the third teeth 720 have a thirdsmoothness smoother than the first smoothness, a third hardness harderthan the first hardness, a wear resistant coating, and/or one or moreadditional and/or alternative characteristics enabling the third teeth720 to have the third wear resistance. In the illustrated embodiment,the third teeth 720, including the third load flank surfaces 722, arehigh carbon, alloyed steel. In some embodiments, the third teeth 720,including the third load flank surfaces 722, are titanium alloy. Inother embodiments, the third teeth 720 and/or the third load flanksurfaces 722 are other materials.

In the illustrated embodiment, the fourth section 706 includes apredetermined number of the teeth 314. For example, the fourth section706 of FIG. 10 includes nine of the teeth 314.

In other embodiments, the fourth section 706 includes other numbers ofthe teeth 314 (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 10, 11, etc.). The teeth314 of the fourth section 706 are referred to herein as fourth teeth724.

The fourth teeth 724 are disposed consecutively on the fourth section706. Thus, the fourth teeth 724 are the outer link teeth 340 and theinner link teeth 342 alternating with the outer link teeth 340.Therefore, consecutive teeth of the fourth teeth 724 have differentthicknesses. For example, a first one of the fourth teeth 724 may be aninner link tooth 342 having a first tooth width WO1, and a second one ofthe fourth teeth 724 disposed consecutively with the first one of thefourth teeth 724 may have the fourth tooth width WO4 greater than thefirst tooth width WO1.

In the illustrated embodiment, the fourth teeth 724 and, particularly, afourth load flank surface 726 of each of the fourth teeth 724 have thefirst wear resistance. In some embodiments, the fourth load flanksurfaces 726 of the fourth teeth 724 have the first smoothness, thefirst hardness, and/or one or more additional and/or alternativecharacteristics enabling the fourth teeth 724 to have the first wearresistance. In the illustrated embodiment, the fourth teeth 724,including the fourth load flank surfaces 726, are heat treated, wroughtaluminum alloy. In other embodiments, the fourth teeth 724 are othermaterials.

FIG. 11 is a front view of the chainring 302 of FIG. 3 decoupled fromthe carrier 308 and the first crank arm 306. However, the longitudinalaxis 316 of the first crank arm 306 is shown in FIG. 11. As discussedabove with reference to FIG. 2, the peak or maximum torque output duringa pedaling cycle employing the crank assembly 300 of FIG. 3 occursduring a maximum torque portion of the pedaling cycle in which thelongitudinal axis 316 of the first crank arm 306 is horizontal or nearlyhorizontal as the rider pedals the first crank arm 306. As a result, atleast one of the teeth 314 which engage and advance the chain 304 duringthe maximum torque portion of the pedaling cycle apply a maximum forceto the chain 304 during the pedaling cycle.

In this disclosure, a tooth is disposed on a chainring “behind” alongitudinal axis of a crank arm by an angle measured in a directionopposite a driving direction from the longitudinal axis of the firstcrank arm 306, where the angle has a vertex at an intersection of thelongitudinal axis of the crank arm and an axis of rotation (e.g., theaxis of rotation 317 of FIG. 11) of the chainring 302. In thisdisclosure, a tooth is disposed on a chainring “in front of” alongitudinal axis of a crank arm by an angle measured in the drivingdirection from the longitudinal axis of the crank arm, where the anglehas a vertex at the intersection of the longitudinal axis of the crankarm and the axis of rotation of the chainring.

As referred to in the present disclosure, a tooth that is behind alongitudinal axis of a crank arm relative to the driving direction bybetween more than zero degrees and 180 degrees or less are referred toin this patent as “trailing” the longitudinal axis of the crank arm. Atooth that is behind the longitudinal axis of the crank arm relative tothe driving direction by more than 180 degrees and less than 360 degreesis referred to in this patent as “leading” the longitudinal axis of thecrank arm.

As discussed above with reference to FIG. 2, during a pedaling cycle ofthe crank assembly 300 of FIGS. 10 and 11, the first crank arm 306 movesfrom the first position 202 (FIG. 2A) to the third position 204 (FIG.2C). As a result, during the pedaling cycle of the first crank arm 306,the first teeth 708 of the first section 700, the second teeth 714 ofthe second section 702, and the fourth teeth 724 of the fourth section706 sequentially engage the chain 304. The second teeth 714 arepositioned on the chainring 302 to engage the chain 304 and apply amaximum force to the chain 304 when the first crank arm 306 is in ornear the third position 206 (FIG. 2B). Thus, in the illustratedembodiment, the second teeth 714 of the second section 702 of thechainring 302 are in positions on the chainring 302 relative to thefirst crank arm 306 to enable at least one of the second teeth 714 toengage the chain 304 and apply the maximum force to the chain 304 duringthe maximum torque portion of the pedaling cycle of the first crank arm306. For example, in the embodiment of FIG. 11, the second teeth 714 areconsecutively disposed on the chainring 302 between about an angle X andabout an angle Y behind the longitudinal axis 316 of the first crank arm306 relative to the driving direction DD. In the illustrated embodiment,angle X is about 85 degrees, and angle Y is about 155 degrees. In otherembodiments, the second teeth 714 are disposed on the chainring 302behind the longitudinal axis 316 of the first crank arm 306 relative tothe driving direction DD by other numbers of degrees such as, forexample, between more than 60 degrees and less than 180 degrees, between30 degrees and 210 degrees, between 60 degrees and 90 degrees, and/or byother number of degrees. As mentioned above, the second teeth 714 areconsecutively disposed on the chainring 302 between about 85 degrees andabout 155 degrees behind the longitudinal axis 316 of the first crankarm 306 relative to the driving direction DD. Thus, the second teeth 714span an arc length corresponding to about 7/36 of a circumference of thepitch circle 344 of the chainring 302 measured from the pitch point 728of an initial one of the second teeth 714 to the pitch point 728 of alast one of the second teeth 714 relative to the driving direction DD.In other embodiments, the second teeth 714 span other arc lengths. Forexample, the second teeth 714 may span arc lengths corresponding tobetween one twelfth and one third of the circumference of the pitchcircle 344 of the chainring 302.

FIG. 12 is a similar view of the chainring 302 shown in FIG. 11. Thefirst teeth 708 of FIG. 11 are in positions on the chainring 302 toenable the first teeth 708 to engage the chain 204 and apply a minimumforce to the chain 304 when the first crank arm 306 is in or near thefirst position 202 (FIG. 2A). Thus, in the present embodiment, the firstteeth 708 of the first section 700 are in positions on the chainring 302relative to the first crank arm 306 to enable at least one of the firstteeth 708 to engage the chain 304 and apply a minimum force to the chain304 during the initial minimum torque portion of the pedaling cycle ofthe first crank arm 306. For example, the first teeth 708 areconsecutively disposed on the chainring 302 between about an angle A infront of the longitudinal axis 316 and about an angle B behind thelongitudinal axis 316 of the first crank arm 306 relative to the drivingdirection DD. In the illustrated embodiment, angle A is about 12 degreesand angle B is about 73 degrees. In other embodiments, the first teeth708 are in other positions relative to the first crank arm 306. Thus,the first teeth 708 span an arc length corresponding to about 3/14 ofthe circumference of the pitch circle 344 of the chainring 302 measuredfrom the pitch point 728 of an initial one of the first teeth 710 to thepitch point 728 of a last one of the first teeth 708 relative to thedriving direction DD. In other embodiments, the first teeth 710 spanother arc lengths.

In the embodiment of FIG. 12, the fourth section 706 is a mirror imageof the first section 700 and is diametrically opposed to the firstsection 700. As a result, the fourth teeth 724 are in positions on thechainring 302 to enable the fourth teeth 724 to apply the minimum forceas the first crank arm 306 moves past the third or horizontal position206 (FIG. 2B) and into the second position 204 (FIG. 2C). Thus, in theillustrated embodiment, the fourth teeth 724 of the fourth section 706are in positions on the chainring 302 relative to the first crank arm306 to enable at least one of the fourth teeth 724 to engage the chain304 and apply the minimum force to the chain 304 during the subsequentminimum torque portion of the pedaling cycle of the first crank arm 306.

During a pedaling cycle of the second crank arm 307 of the crankassembly 300, the second crank arm 307 moves from the first position 202(FIG. 2A) to the third position 204 (FIG. 2C). As a result, during thepedaling cycle, the fourth teeth 724 of the fourth section 706, thethird teeth 720 of the third section 704, and the first teeth 708 of thefirst section 700 sequentially engage the chain 304. In the illustratedembodiment, the third section 704 is a mirror image of the secondsection 702, the first section 700 is a mirror image of the fourthsection 706, and the second crank arm 307 is a mirror image of the firstcrank arm 306. Further, the third section 704 is diametrically opposedto the second section 702. Therefore, the description above of thepositions of the second teeth 714 relative to the first crank arm 306are applicable to positions of the third teeth 720 relative to thesecond crank arm 307. As a result, during the pedaling cycle of thesecond crank arm 307, the fourth teeth 724 engage the chain 304 andapply a minimum force to the chain 304 during the initial minimum torqueportion of the pedaling cycle of the second crank arm 307; the thirdteeth 720 engage the chain 304 and apply the maximum force to the chain304 during the maximum torque portion of the pedaling cycle of thesecond crank arm 307; and the first teeth engage the chain 304 and applya minimum force to the chain 304 during the subsequent minimum torqueportion of the pedaling cycle of the second crank arm 307.

Turning to FIG. 13, an outboard side 730 of the chainring 302 isdepicted with the second section 702 and the third section 704 decoupledfrom the body 310. In the illustrated embodiment, the periphery 312 ofthe body 310 of the chainring 302 has a first peripheral portion 732, asecond peripheral portion 734, a third peripheral portion 736, and afourth peripheral portion 738. The first peripheral portion 732 isintegrally formed and/or unitary with the first teeth 710, and thefourth peripheral portion 738 is integrally formed and/or unitary withthe fourth teeth 724.

The second peripheral portion 734 of FIG. 12 has no teeth. In theillustrated embodiment, the second peripheral portion 734 includes afirst seating area 740 on the outboard side 730 of the chainring 302 toreceive the first bracket 712 (see FIG. 10). With reference to theembodiment of FIG. 12, the first seating area 740 is a recess having asize and a shape corresponding to a size and shape of the first bracket712. The third peripheral portion 736 also has no teeth. In theillustrated embodiment, the third peripheral portion 736 includes asecond seating area 742 to receive the second bracket 718 (see FIG. 10).In the illustrated embodiment, the second seating area 742 is a recesshaving a size and a shape corresponding to a size and shape of thesecond bracket 718. In other embodiments, the first seating area 740and/or the second seating area 742 are implemented in other ways.

FIG. 14 illustrates an inboard side 744 of the chainring 302 with thesecond section 702 and the third section 704 decoupled from the body310. In the illustrated embodiment, on the inboard side 744 of thechainring 302, the second peripheral portion 734 and the thirdperipheral portion 736 do not include seating areas for the firstbracket 712 and the second bracket 718, respectively. In otherembodiments, the second peripheral portion 734 and/or the thirdperipheral portion 736 include seating areas (e.g., recesses) to receiveportions of the first bracket 712 and/or the second bracket 718,respectively,

FIG. 15 is a perspective view of one embodiment of the second section702 of the chainring 302. In the illustrated embodiment, the firstbracket 712 includes an arc-shaped flange 746. When the second section702 is coupled to the body 310 of the chainring 302, the flange 746 isreceived in the first seating area 740 of the second peripheral portion734 of the body 310.

Portions of the second teeth 714 extend or project from the flange 746to form an overhanging base 748. When the second section 702 is coupledto the body 310, the base 748 rests on and/or is supported by theperiphery 312 of the body 310, and an inboard facing side 750 of theflange 746 abuts the first seating area 740. In the present embodimentof the chainring 302, the third section 704 is substantially similar oridentical to the second section 702 of FIG. 15. Therefore, the abovedescription of the second section 702 is applicable to the third section704. Therefore, to avoid redundancy, the third section 704 of thechainring 302 is not separately described herein.

FIG. 16 is another embodiment of a chainring 800 disclosed herein, whichmay be used to implement the crank assembly 112 of FIG. 1 and/or thecrank assembly 300 of FIG. 3. In the illustrated embodiment, thechainring 800 includes a first section 802, a second section 804, athird section 806, and a fourth section 808. In the illustratedembodiment, the first section 802 is a mirror image of the fourthsection 808, and the first section 802 is diametrically opposed to thefourth section 808. The third section 806 is a mirror image of thesecond section 804, and the third section 806 is diametrically opposedto the second section 804.

In the illustrated embodiment, the first section 802 has consecutivefirst teeth 810 having a first wear resistance. The second section 804has consecutive second teeth 812 having a second wear resistance greaterthan the first wear resistance. The third section 806 has consecutivethird teeth 814 having a third wear resistance. In some embodiments, thethird wear resistance is substantially equal to the second wearresistance. In some embodiments, the third wear resistance is less thanor greater than the second wear resistance. The fourth section 808 hasconsecutive fourth teeth 816 having the first wear resistance.

In the illustrated embodiment, the first teeth 810, the second teeth812, the third teeth 814, and the fourth teeth 816 have substantiallythe same size and shape. For example, the first teeth 810, the secondteeth 812, the third teeth 814, and the fourth teeth 816 havesubstantially the same thickness. In the illustrated embodiment, thefirst section 802 and the fourth section 808 are integrally formedand/or unitary with a body 818 of the chainring 800. The second section804 is coupled to the body 818 via three first fasteners 820. The thirdsection 806 is also coupled to the body 818 via three second fasteners822. In other embodiments, the second section 804 and/or the thirdsection 806 are coupled to the body 818 via other numbers of fasteners(e.g., 1, 2, 4, 5, etc.).

When a crank arm (e.g., the crank arm 124 of FIG. 1, the first crank arm306 of FIG. 3, and/or the second crank arm 307 of FIG. 3) is coupled tothe chainring 800 of FIG. 16, the second teeth 812 of the second section804 and/or the third teeth 814 of the third section 806 are in positionson the chainring 800 relative to the crank arm to enable at least one ofthe second teeth 812 and/or the third teeth 814 to engage a chain (e.g.,the chain 304) and apply a maximum force to the chain during the maximumtorque portion of the pedaling cycle of the chainring 800. The firstteeth 810 of the first section 802 are in positions on the chainring 302relative to the crank arm to enable at least one of the first teeth 810to engage the chain and apply a minimum force to the chain 304 duringone of the initial minimum torque portion the pedaling cycle of thechainring 800. The fourth teeth 816 of the fourth section 808 are inpositions on the chainring 800 relative to the crank arm to enable atleast one of the fourth teeth 816 to engage the chain and apply theminimum force to the chain during the subsequent minimum torque portionof the pedaling cycle of the chainring 800.

FIG. 17 is an exploded view of the chainring 800 of FIG. 8. In theillustrated embodiment, the body 818 of the chainring 800 includes aperipheral potion 824 having no teeth. The peripheral portion 824 of thechainring 800 supports the second section 804. In the illustratedembodiment, the peripheral portion 824 does not include a recess toreceive the second section 804.

FIG. 18 is a cross-sectional view of the body 818 and the second section804 along line 17-17 of FIG. 16. FIG. 18 illustrates the second section804 supported on the peripheral portion 824 of the body 818. In theillustrated embodiment, the second section 804 includes an L-shapedbracket 826 that is supported on the peripheral portion 826. In otherembodiments, the bracket 826 is other shapes. For example, the bracket826 may be U-shaped.

FIG. 19 shows another embodiment of a crank assembly 900. In theillustrated embodiment, the crank assembly 900 includes a chainring 902,a carrier 904, a first crank arm 906, and a second crank arm 908. Thefirst crank arm 906, the second crank arm 908, and the chainring 902rotate about an axis of rotation 910 during a pedaling cycle of thecrank assembly 900. The axis of rotation 910 extends into the page fromthe perspective of FIG. 19. The first crank arm 906 includes a firstlongitudinal axis 912 that intersects the axis of rotation 910. Thesecond crank arm 906 includes a second longitudinal axis 914 that isparallel to the first longitudinal axis 912 and intersects the axis ofrotation 910.

In the illustrated embodiment, the carrier 904 includes a first arm 916,a second arm 918, a third arm 920, and a fourth arm 922. In otherembodiments, the carrier 904 includes other numbers of arms (e.g., 1, 2,3, 5, 6, etc.). in the illustrated embodiment, the first arm 916, thesecond arm 918, the third arm 920, and the fourth arm 922 extendradially from a hub 924 of the carrier 904. The first crank arm 906 andthe second crank arm 908 are non-rotatably coupled to the hub 924 of thecarrier 904.

The chainring 902 includes a first section or bridge 926, a secondsection or bridge 928, a third section or bridge 930, and a fourthsection or bridge 932. In the illustrated embodiment, the first bridge926 includes consecutive first teeth 934, the second bridge 928 includesconsecutive second teeth 936, the third bridge 928 includes consecutivethird teeth 938, and the fourth bridge 930 includes consecutive fourthteeth 940. In some embodiments, the first teeth 934, the second teeth936, the third teeth 938, and/or the fourth teeth 940 are alternatingouter link teeth and inner link teeth, which may have shapes and/orsizes similar or identical to those described herein, e.g., the outerlink teeth 340 of FIG. 5, the outer link teeth 400 of FIG. 7, the outerlink teeth 500 of FIG. 8, the outer link teeth 600 of FIG. 9, and/or theinner link teeth 342 of FIGS. 5 and 6.

In the illustrated embodiment, the first bridge 926 extends across afirst space 942 between the first arm 916 of the carrier 904 and thesecond arm 918 of the carrier 904. The second bridge 928 extends acrossor bridges a second space 944 between the second arm 918 and the thirdarm 920. The third bridge 930 bridges a third space 946 between thefirst arm 916 and the fourth arm 922. The fourth bridge 932 extendsacross a fourth space 948 between the third arm 920 and the fourth arm922.

A first fastener 950 removably couples the first bridge 926 and thesecond bridge 928 to the second arm 918 of the carrier 904. A secondfastener 952 removably couples the first bridge 926 and the third bridge930 to the first arm 916 of the carrier 904. A third fastener 954removably couples the second bridge 928 and the fourth bridge 932 to thethird arm 920 of the carrier 904. A fourth fastener 956 removablycouples the third bridge 930 and the fourth bridge 932 to the fourth arm922 of the carrier 904. Thus, each of the bridges 926, 928, 930, 932 maybe individually decoupled from the crank assembly 900. As a result,unlike traditional chainrings which must be replaced in their entiretywhen merely a few teeth reach an end of their useful life, the examplechainring 902 of FIG. 19 enables selected ones of the bridges 926, 928,930, 932 to be replaced.

In the illustrated embodiment, the first teeth 934 and, particularly, afirst load flank surface 958 of each of the first teeth 934 have a firstwear resistance. In some embodiments, the first load flank surfaces 958of the first teeth 934 have a first smoothness, a first hardness, and/orone or more additional and/or alternative characteristics enabling thefirst teeth 934 to have the first wear resistance. In the illustratedembodiment, the first bridge 926, including the first teeth 934, areheat treated, wrought aluminum alloy. In other embodiments, the firstbridge 926 and/or the first teeth 934 are other materials.

In the illustrated embodiment, the second teeth 936 and, particularly, asecond load flank surface 960 of each of the second teeth 936 have asecond wear resistance greater than the first wear resistance. In someembodiments, the second load flank surfaces 960 of the second teeth 936have a second smoothness smoother than the first smoothness, a secondhardness harder than the first hardness, a wear resistant coating,and/or one or more additional and/or alternative characteristicsenabling the second teeth 936 to have the second wear resistance. In theillustrated embodiment, the second bridge 928, including the secondteeth 936, is high carbon, alloyed steel. In some embodiments, thesecond bridge 928, including the second teeth 936, is titanium alloy. Inother embodiments, the second bridge 928 and/or the second teeth 936 areother materials.

In the illustrated embodiment, the third teeth 938 and, particularly, athird load flank surface 962 of each of the third teeth 938 have a thirdwear resistance greater than the first wear resistance. In someembodiments, the third wear resistance is greater than the second wearresistance. In other embodiments, the third wear resistance is less thanthe second wear resistance. In still other embodiments, the third wearresistance is equal to the second wear resistance. In some embodiments,the third load flank surfaces 962 of the third teeth 938 have a thirdsmoothness smoother than the first smoothness, a third hardness harderthan the first hardness, a wear resistant coating, and/or one or moreadditional and/or alternative characteristics enabling the third teeth938 to have the third wear resistance. In the illustrated embodiment,the third bridge 930, including the third teeth 938, is high carbon,alloyed steel. In some embodiments, the third teeth 938, including thethird load flank surfaces 962, are titanium alloy. In other embodiments,the third bridge 930 and/or the third teeth 938 are other materials.

In the illustrated embodiment, the fourth teeth 940 and, particularly, afourth load flank surface 964 of each of the fourth teeth 940 have afourth wear resistance. In some embodiments, the fourth load flanksurfaces 964 of the fourth teeth 940 have the a fourth smoothness, afourth hardness, and/or one or more additional and/or alternativecharacteristics enabling the fourth teeth 940 to have the fourth wearresistance. In some embodiments, the fourth wear resistance is equal tothe first wear resistance. In other embodiments, the fourth wearresistance is greater than or less than the first wear resistance. Inthe illustrated embodiment, fourth bridge 932, including the fourthteeth 740 are heat treated, wrought aluminum alloy. In otherembodiments, the fourth bridge 932 is other materials.

In the illustrated embodiment, the second teeth 936 of the second bridge928 are in positions on the chainring 902 relative to the first crankarm 906 to enable at least one of the second teeth 936 to engage a chain(e.g., the chain 304) and apply a maximum force to the chain during amaximum torque portion of a pedaling cycle of the first crank arm 906.For example, the second teeth 936 may be consecutively disposed on thechainring 902 between a first predetermined angle (e.g., Angle 1 of FIG.19) and a second predetermined angle (e.g., Angle 2 of FIG. 19) behindthe first longitudinal axis 912 of the first crank arm 906 relative to adriving direction DD. For example, the second teeth 936 may beconsecutively disposed on the chainring 902 between about 45 degrees andabout 130 degrees behind the first longitudinal axis 912 of the firstcrank arm 906 relative to a driving direction DD. In other embodiments,the second teeth 936 are disposed on the chainring 902 behind thelongitudinal axis 912 of the first crank arm 906 relative to the drivingdirection DD by other numbers of degrees such as, for example, betweenmore than 60 degrees and less than 180 degrees, between 30 degrees and210 degrees, between 60 degrees and 90 degrees, and/or by other numberof degrees.

The third teeth 938 of the third bridge 930 are in positions on thechainring 902 relative to the second crank arm 908 to enable at leastone of the second teeth 938 to engage the chain and apply a maximumforce to the chain during a maximum torque portion of a pedaling cycleof the second crank arm 908. For example, the third teeth 938 may beconsecutively disposed on the chainring 902 between a thirdpredetermined angle (e.g., angle 3 of FIG. 19) and a fourthpredetermined angle (e.g., angle 4 of FIG. 19) behind the secondlongitudinal axis 914 of the second crank arm 908 relative to thedriving direction DD. In some embodiments, the third predetermined angleand/or the fourth predetermined angle are the same as the firstpredetermined angle and the second predetermined angle, respectively. Inother embodiments, the third predetermined angle and/or the fourthpredetermined angle are different than the first predetermined angleand/or the second predetermined angle, respectively.

The first teeth 934 of the first bridge 926 are in positions on thechainring 902 relative to the first crank arm 906 to enable at least oneof the first teeth 934 to engage the chain and apply a minimum force tothe chain during an initial minimum torque portion of the pedaling cycleof the first crank arm 906. Further, the first teeth 934 of the firstbridge 926 are in positions on the chainring 902 relative to the secondcrank arm 908 to enable at least one of the first teeth 934 to engagethe chain and apply a minimum force to the chain during a subsequentminimum torque portion of the pedaling cycle of the second crank arm908. For example, the first teeth 934 are consecutively disposed on thechainring 902 between a fifth predetermined angle (e.g., Angle 5 of FIG.19) in front of the first longitudinal axis 912 of the first crank arm906 and sixth predetermined angle (e.g., Angle 6 of FIG. 19) behind thefirst longitudinal axis 712 of the first crank arm 906 relative to thedriving direction DD. For example, the fifth predetermined angle may beabout 40 degrees and the sixth predetermined angle may be about 40degrees. In other embodiments, the first teeth 708 are in otherpositions relative to the first crank arm 906.

The fourth teeth 940 of the fourth bridge 932 are in positions on thechainring 902 relative to the first crank arm 906 to enable at least oneof the fourth teeth 940 to engage the chain and apply a minimum force tothe chain during the subsequent minimum torque portion of the pedalingcycle of the first crank arm 906. Further, the fourth teeth 940 of thefourth bridge 932 are in positions on the chainring 902 relative to thesecond crank arm 908 to enable at least one of the fourth teeth 940 toengage the chain and apply a minimum force to the chain during thesubsequent minimum torque portion of the pedaling cycle of the secondcrank arm 908. For example, the fourth teeth 940 may be consecutivelydisposed on the chainring 902 between a seventh predetermined angle(e.g., Angle 7 of FIG. 19) in front of the second longitudinal axis 914and an eighth predetermined angle (e.g., Angle 8 of FIG. 19) behind thesecond longitudinal axis 914 of the second crank arm 908 relative to thedriving direction DD. In some embodiments, the seventh predeterminedangle and/or the eighth predetermined angle are the same as the fifthpredetermined angle and the sixth predetermined angle, respectively. Insome embodiments, the seventh predetermined angle and/or the eighthpredetermined angle are different than the fifth predetermined angleand/or the sixth predetermined angle, respectively.

FIG. 20 is a cross-sectional view of the chainring 902 and the carrier904 along line 20-20 of FIG. 19. FIG. 20 illustrates an example joint966 removably coupling the second bridge 928 and the fourth bridge 932to the third arm 920 of the carrier 904. In the illustrated embodiment,the third arm 920 overlaps the second bridge 928 and the fourth bridge932 such that a first aperture 968 of the second bridge 928, a secondaperture 970 of the fourth bridge 932, and a third aperture 972 of thethird arm 920 are substantially coaxial. The third fastener 954 extendsthrough the second bridge 928, the fourth bridge 932, and the third arm920 of the carrier 904 via the first aperture 968, the second aperture970, and the third aperture 972, respectively. The third fastener 954 ofFIG. 20 includes a bolt 974 and a nut 976 threaded to the bolt 974. Inother embodiments, the joint 966 employs one or more additional and/oralternative types of fasteners.

FIG. 21 is a different embodiment of a chainring 1000, which may be usedto implement any of the disclosed crank assemblies, e.g., the examplecrank assembly 112 of FIG. 1, the example crank assembly 300 of FIG. 3,and/or the example crank assembly 900 of FIG. 19. In the illustratedembodiment, the chainring 1000 includes a body 1002. The chainring 1000includes consecutive first teeth 1004 and consecutive second teeth 1006disposed on a periphery 1008 of the body 1002. Each of the first teeth1004 includes a first tooth body 1010 and a first load flank surface1012. Each of the second teeth 1006 includes a second tooth body 1014and an insert 1016 coupled to the second tooth body 1014. In theillustrated embodiment, each of the inserts 1016 forms a respectivesecond load flank surface 1018 of the second teeth 1006. The inserts1016 of FIG. 20 do not cover respective rear flank surfaces 1020 of thesecond teeth 1006. In other embodiments, the inserts 1016 cover the rearflank surfaces 1020 of the second teeth 1006.

In the illustrated embodiment, the first teeth 1004, including the firsttooth bodies 1010 and the first load flank surfaces 1012, and the secondtooth bodies 1014 are integrally formed and/or unitary. For example, thefirst teeth 1004, including the first tooth bodies 1010 and the firstload flank surfaces 1012, and the second tooth bodies 1014 may bestamped from a single piece of a first material such as, for example,aluminum alloy. In other embodiments, the first teeth 1004, includingthe first tooth bodies 1010 and the first load flank surfaces 1012, andthe second tooth bodies 1014 may be formed from a single piece of amaterial different than aluminum alloy and/or from two or more pieces.In some embodiments, the first load flank surfaces 1012 of the firstteeth 1004 have a first wear resistance. In some embodiments, the firstload flank surfaces 1012 of the first teeth 1004 have a firstsmoothness, a first hardness, and/or one or more additional and/oralternative characteristics enabling the first load flank surfaces 1012to have the first wear resistance.

In the illustrated embodiment, the inserts 1016 are a second materialdifferent than the first material. For example, the inserts 1016 may behigh carbon, alloyed steel; titanium alloy; and/or one or moreadditional and/or alternative materials. As a result, the second loadflank surfaces 1018 formed by the inserts 1016 have a second wearresistance greater than the first wear resistance. In some embodiments,the second load flank surfaces 1018 of the second teeth 1006 have asecond smoothness smoother than the first smoothness, a second hardnessharder than the first hardness, a wear resistant coating, and/or one ormore additional and/or alternative characteristics enabling the secondteeth 1006 to have the second wear resistance.

The first crank arm 906, the second crank arm 908, and the carrier 904of FIG. 19 may be coupled to the chainring 1000 to form a crankassembly. In such embodiments, the second teeth 1006 of the chainring1000 may be positioned relative to the crank arm 906 to enable at leastone of the second teeth 1006 to engage a chain 1022 and apply a maximumforce to the chain 1022 during a maximum torque portion of the pedalingcycle of the first crank arm 906. For example, the second teeth 1006 maybe consecutively disposed on the chainring 1000 between a firstpredetermined angle and a second predetermined angle behind the firstlongitudinal axis 912 of the first crank arm 906 relative to the drivingdirection DD as indicated in FIG. 19 by Angle 1 and Angle 2,respectively.

The first teeth 1004 are in positions on the chainring 1000 relative tothe first crank arm 906 to enable at least one of the first teeth 1004to engage the chain 1022 and apply a minimum force to the chain 1022during the initial subsequent torque portion of the pedaling cycle ofthe first crank arm 906. Further, the first teeth 1004 are in positionson the chainring 1000 relative to the second crank arm 908 to enable atleast one of the first teeth 1004 to engage the chain 1022 and apply aminimum force to the chain 1022 during the initial minimum torqueportion of the pedaling cycle of the second crank arm 908. For example,the first teeth 1004 may be consecutively disposed on the chainring 1000between a third predetermined angle in front of the first longitudinalaxis 912 of the first crank arm 906 relative to the driving direction DDand a fourth predetermined angle behind the first longitudinal axis 912of the first crank arm 906 relative to the driving direction DD asindicated in FIG. 19 by Angle 7 and Angle 8, respectively.

FIG. 22 is a perspective view of another example chainring 1100disclosed herein. In the illustrated embodiment, the chainring 1100includes a body 1102 having a periphery 1104. Teeth 1106 areconsecutively disposed on the periphery 1104. Each of the teeth 1106 ofFIG. 22 includes a tooth body 1108 and an insert 1110 coupled to thetooth body 1108. Each of the inserts 1110 forms a load flank surface1112 for each of the teeth 1106.

In the illustrated embodiment, the tooth bodies 1108 and the body 1102of the chainring 1100 are integrally formed and/or unitary. For example,the tooth bodies 1108 and the body 1102 of the chainring 1100 may bestamped from a single piece of a first material such as, for example,aluminum alloy. In other embodiments, the tooth bodies 1108 and body1102 may be formed from a single piece of a material different thanaluminum alloy and/or from two or more pieces.

In the illustrated embodiment, the inserts 1110 are a second materialdifferent than the first material. For example, the inserts 1110 may behigh carbon, alloyed steel; titanium alloy; and/or one or moreadditional and/or alternative materials. As a result, the load flanksurfaces 1112 formed by the inserts 1110 have a wear resistance greaterthan if the load flank surfaces 1112 were formed from the firstmaterial. In some embodiments, the load flank surfaces 1112 have apredetermined smoothness, a predetermined hardness, a wear resistantcoating, and/or one or more additional and/or alternativecharacteristics enabling the teeth 1106 to have the wear resistance.

Numerous modifications to the embodiments disclosed herein will heapparent to those skilled in the art in view of the foregoingdescription. For example, any of the embodiments disclosed herein may bemodified to include any of the structures or/or methodologies disclosedin connection with different embodiments. Accordingly, this disclosureis to be construed as illustrative only and is presented for the purposeof enabling those skilled in the art to make and use the invention andto teach the best mode of carrying out same. The exclusive rights to allmodifications which come within the scope of the appended claims arereserved.

1. A chainring, comprising: a first section including consecutive firstteeth, each of the first teeth including a first load flank surfacehaving a first wear resistance; and a second section coupled to thefirst section, the second section including consecutive second teeth,each of the second teeth including a second load flank surface having asecond wear resistance greater than the first wear resistance, whereinthe consecutive second teeth span an arc length corresponding to betweenone twelfth and one third of a circumference of a pitch circle of thechainring.
 2. The chainring of claim 1 further comprising a thirdsection including consecutive third teeth, each of the third teethincluding a third load flank surface having a third wear resistancegreater than the first wear resistance, wherein the third section isdiametrically opposed to the second section.
 3. The chainring of claim2, wherein the third wear resistance is equal to the second wearresistance.
 4. The chainring of claim 2, wherein the third teeth span anarc length corresponding to between one twelfth and one third of thecircumference of the pitch circle of the chainring.
 5. The chainring ofclaim 2 further comprising a fourth section including consecutive fourthteeth, each of the fourth teeth including a fourth load flank surfacehaving the first wear resistance.
 6. The chainring of claim 5, whereinthe fourth section is diametrically opposed to the first section.
 7. Thechainring of claim 1, wherein the first section is removably coupled toa first portion of the chainring.
 8. The chainring of claim 7, whereinthe second section is removably coupled to a second portion of thechainring.
 9. A chainring, comprising: a first tooth including a firstload flank surface of a first wear resistance; a second tooth having asecond load flank surface of a second wear resistance greater than thefirst wear resistance; and a third tooth disposed consecutively with thesecond tooth, the third tooth having a third load flank surface of thesecond wear resistance, wherein the second tooth has a differentthickness than the third tooth.
 10. The chainring of claim 9 furthercomprising a body having a first peripheral portion and a secondperipheral portion, the first peripheral portion integrally formed withthe first tooth, the second peripheral portion including no teeth. 11.The chainring of claim 10 further comprising a bracket including thesecond tooth, the bracket disposed on the second peripheral portion ofthe body.
 12. The chainring of claim 9, wherein the second toothincludes a protrusion extending from a side of the second tooth.
 13. Thechainring of claim 9, wherein the first tooth has substantially the samethickness as the second tooth.
 14. The chainring of claim 9, wherein afirst top land of the first tooth has a different thickness than asecond top land of the second tooth.
 15. A crank assembly comprising: achainring having first teeth and second teeth, the first teeth eachincluding a first load flank surface of a first wear resistance, thesecond teeth each including a second load flank surface of a second wearresistance greater than the first wear resistance; and a crank armcoupled to the chainring, wherein the second teeth are consecutivelydisposed on the chainring between more than 60 degrees and less than 110degrees behind a longitudinal axis of the crank arm relative to adriving direction.
 16. The crank assembly of claim 15, wherein thechainring includes a body having a first peripheral portion in which thefirst teeth are unitary therewith and a second peripheral portion thatincludes no teeth.
 17. The crank assembly of claim 16, wherein thechainring includes a bracket including the second teeth, the bracketsupported on the second peripheral portion of the ring.
 18. The crankassembly of claim 15, further comprising a wear-resistant coating oneach of the second teeth.
 19. The crank assembly of claim 15, furthercomprising an insert coupled to each of the second teeth, each of theinserts forming a respective one of the second load flank surfaces. 20.The crank assembly of claim 15, further comprising a carrier coupled tothe chainring, the carrier coupled to the crank arm.
 21. The crankassembly of claim 20, wherein the chainring includes a first section anda second section coupled to the first section, the first sectionincluding the first teeth, the second section including the secondteeth, and wherein an arm of the carrier overlaps the second section.22. The crank assembly of claim 21, wherein a fastener extends throughthe carrier and the second section.
 23. The crank assembly of claim 15further comprising a second crank arm coupled to the chainring, whereinthe chainring includes third teeth each having a third load flanksurface of the second wear resistance, the third teeth disposed on thechainring between more than 60 degrees and less than 110 degrees behinda longitudinal axis of the second crank arm in the driving direction.24. A crank assembly, comprising: a crank arm; and only one chainringcoupled to the crank arm, the chainring including a first tooth and asecond tooth, the first tooth including a first load flank surfacehaving a first wear resistance, the second tooth including a second loadflank surface having a second wear resistance greater than the firstwear resistance, the second tooth in a position on the chainringrelative to the crank arm that is to enable the second tooth to apply amaximum force to a chain during a maximum torque portion of a pedalingcycle of the crank arm.
 25. The crank assembly of claim 24, wherein thefirst tooth is in a position on the chainring relative to the crank armthat is to enable the first tooth to apply a minimum force to the chainduring a minimum torque portion of the pedaling cycle of the crank arm.26. The crank assembly of claim 24, further comprising a carrier coupledto the chainring, the carrier including a first arm, a second arm, and athird arm.
 27. The crank assembly of claim 26, wherein the chainringincludes a first bridge and a second bridge removably coupled to thefirst bridge, the first bridge including the first tooth and supportedby the first arm and the second arm, the second bridge including thesecond tooth and supported by the second arm and the third arm.
 28. Thecrank assembly of claim 24, wherein the second tooth includes an insertforming the second load flank surface of the second tooth.
 29. Achainring comprising: a body having a first tooth and a second tooth,the first tooth having a first load flank surface of a first wearresistance; and an insert coupled to the second tooth and forming asecond load flank surface of the second tooth, the second load flanksurface having a second wear resistance greater than the first wearresistance.
 30. The chainring of claim 29, wherein the insert does notcover a rear flank surface of the second tooth.
 31. The chainring ofclaim 30, wherein the first load flank surface of the first tooth andthe body of the second tooth are of the same material.
 32. The chainringof claim 31, wherein the insert is a different material than the body.33. A crank assembly comprising: a first section of a chainringincluding first teeth of a first material; a second section of thechainring coupled to the first section, the second section includingsecond teeth of a second material different than the first material; anda carrier including an arm overlapping the second section of thechainring.
 34. The crank assembly of claim 33, wherein the arm overlapsthe first section of the chainring.
 35. The crank assembly of claim 34further comprising a fastener extending through the first section, thesecond section, and the carrier.
 36. The crank assembly of claim 33,wherein the carrier includes a second arm, the first section bridging afirst space between the arm and the second arm.
 37. The crank assemblyof claim 36, wherein the carrier includes a third arm, the secondsection bridging a space between the arm and the third arm.
 38. Thecrank assembly of claim 33 further comprising a crank arm coupled to thecarrier, wherein the second teeth of the second section are provided onthe chainring in a manner to trail a longitudinal axis of the crank armin a driving direction of the crank arm.
 39. The crank assembly of claim38 further comprising: a second crank arm coupled to the carrier; and athird section of the chainring coupled to the first section, the thirdsection including third teeth of the second material, wherein the thirdteeth trail a longitudinal axis of the second crank arm in the drivingdirection.